Yep, scala's .net back-end is discontinued, and one of the main challenges (I worked on it a bit) was indeed generating the proper generic signatures. (I hear people are using ikvm these days.)
For more context on why F# does in fact run into problems, see https://visualstudio.uservoice.com/forums/121579-visual-stud.... To my understanding, F# only allows type variables to vary, not type constructors (all generic variables must be escorted by a concrete type), and to go a step further, it doesn't allow type constructors to be used as higher-kinded type variables, which is useful sometimes. I see no reason why these couldn't be implemented on top of the JVM, though.
